This invention relates to a heat-resistant composite body and a process for preparing it. More particularly, this invention is concerned with a composite body for use in heat-resistant jigs that can be suitably used in heat-resistant jigs for electronic industrial uses, for example, in diffusion and oxidation treatments of semiconductors, joining of diodes, glass sealing, and brazing of lead frames of packages.
Hitherto known as materials for heat-resistant jigs for electronic industrial uses are, for example, carbon/silicon carbide composite bodies comprising a silicon carbide film formed on the surface of a graphite substrate, quartz glasses, and composite bodies comprising a silicon carbide molded product filled with metallic silicon, which are used according to their respective purpose.
Incidentally, the above carbon/silicon carbide composite bodies comprising a silicon carbide film formed on the surface of a graphite substrate is required to be subjected to purification treatment by a method in which the graphite substrate is previously applied with a high temperature treatment in a halogen gas atmosphere, or the like method, thus economically disadvantageously costing a great deal. Also, the quartz glass is preferred from the viewpoint of purity, but has a somewhat low thermal resistance to easily cause deformation by softening.
As the composite bodies comprising a silicon carbide molded product filled with metallic silicon, Japanese Patent Publication No. 10825/1979 (U.S. Pat. No. 3,951,587) discloses an invention relating to "a semiconductor diffusion furnace comprising a process tube, a paddle having the dimension and shape with which it can be inserted to the tube, and at least one boat that can be supported by said paddle, wherein said process tube, paddle and boat are mainly composed of a matrix of sintered silicon carbide containing 5 to 30 % by weight of a high purity metallic silicon, and said metallic silicon imparts gas-impermeability to said process tube, paddle and boat. Japanese Unexamined Patent Publication No. 142183/1978 also discloses an invention relating to "a jig for a gas-impermeable silicon wafer, containing 35 to 70 % of silicon carbide and 65 to 30 % of metallic silicon in weight percent."
However, the sintered silicon carbide matrix described in the former Japanese Patent Publication No. 10825/1979 is a recrystallized silicon carbide, using as a starting material relatively so coarse silicon carbide particles as to have a large surface coarseness on its surface, so that not only it is difficult to prepare without applying any particular mechanical working a sintered body that is required to have especially high dimensional precision, but also it can be filled therein with the metallic silicon with an amount of relatively as small as from 5 to 30 % by weight.
On the other hand, the jig for a silicon wafer described in the latter Japanese Unexamined Patent Publication No. 142183/1978 contains metallic silicon in an amount of relatively as large as 30 to 65 % by weight, but Examples in its specification describe a process for preparing a jig obtained by impregnating with metallic silicon a special porous silicon carbide body comprising a molded product mainly comprised of carbon fiber and treated to be made into a silicon product, and a process for preparing a jig according to a reaction sintering method, obtained by heating a mixture comprising silicon carbide powder, metallic silicon powder, phenol resin, etc. The jigs obtained by these preparation processes are considered to be able to satisfy both the economical merits and strength with difficulty.
Incidentally, the heat-resistant jigs for use in electronic industries are mainly used in purpose to handle high purity products such as semiconductors. Accordingly, it is important for them to have a high purity and not to contaminate the products and also having superior wear resistance. Besides this, it is preferable for them to have superior thermal conductivity and thermal shock resistance as they are used in purpose in which heating and cooling are frequently repeated. However, it has been difficult to prepare a heat-resistant jig having such various superior properties.
Under such circumstances, the present inventors have ever developed a heat-resistant jig material that can particularly have superior thermal distribution and obtain uniform thermal distribution and quick heat response as compared with the above-mentioned conventionally known heat-resistant jig materials, and proposed in Japanese Unexamined Patent Publication No. 214424/1986 a heat-resistant jig and a process for preparing it.
However, since in the above invention a porous body obtained by sintering a molded product in which the respective particles of silicon carbide particles are present in a homogeneously dispersed state is impregnated with metallic silicon, there have had to be used silicon carbide powder having very uniform particle diameter in order to obtain a porous body having a markedly high permeable void volume.